Valve tappet



Sept. 6, 1966 J. L. COTTON 3,270,726

VALVE TAPPET Filed Oct. 20, 1965 3 Sheets-Sheet 1 lnvenlor 1 A a A Horney Sept. 6, 1966 J, co To 3,270,726

VALVE TAPPET Filed 001:. 20, 1965 5 Sheets-Sheet 2 Inventor Attorney Sept. 6, 1966 J. L. COTTON 3,270,726

' VALVE TAPPET Filed Oct. 20, 1965 5 Sheets-Sheet :5

lnvenlor v c/orm Jae foZ/an Attorney United States Patent 3,270,726 VALVE TAPPET John Lee Cotton, Flitwick, England, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 20, 1965, Ser. No. 498,953 Claims priority, application Great Britain, Nov. 14, 1964, 46,479/ 64 6 Claims. (Cl. 123-90) This invention relates to tappets or cam followers for valve mechanisms of internal combustion engines.

Various proposals have been made hitherto to make such tappets adjustable so that the opening and closing of each individual valve on the engine can be separately adjusted. Such tappets are interposed between the cam and the end of the valve stem.

An adjustable tappet according to the invention comprises a cup-member which is adapted to fit over the end of the valve stem and which has a transverse threaded bore containing an adjustable screw-plug having a tapered fiat surface for contacting the end of the valve stem.

Preferably a single flat surface is formed on the screwplug so that adjustment of the tappet clearance is effected in steps of single turns of thescrew-plug.

The screw-plug also preferably has an end slot or recess for a screw-driver or squared key so that it can easily be rotated in the transverse threaded bore.

The axis of the threaded bore and the plane of the flat surface of the screw-plug are so disposed relative to the axis of the valve stem, that the fiat surface in its various adjusted positions always fits flush with the end surface of the valve stem.

The scope of the monopoly is defined by the appended claims; the invention and how it can be performed are hereinafter particularly described with reference to the accompanying drawings in which:

FIGURE 1 is a vertical cross-section of the upper part of a cylinder of an internal combustion engine and shows an adjustable tappet in accordance with the invention in its installed operating position;

FIGURE 2 is an enlarged vertical section of the tappet shown in FIGURE 1;

FIGURE 3 is an enlarged part-sectional elevation of the tappet and cam shown in FIGURE 1; and

FIGURE 4 is a plan of the top surface of the tappet.

FIGURE 1 shows parts of an internal combustion engine 10, including a cylinder block 11, on which is mounted a cylinder head 12, fitted with a conventional poppet valve 13, for controlling a port 14, connecting the engine cylinder with the manifold (not shown). The valve 13 has a stem 16. A conventional coil return spring for the valve is also provided. A cover 17, secured to the cylinder head by resilient flanges 18, encloses a rotatable cam shaft 20, one cam 21 of which bears on an adjustable tappet 22 fitted over the end of the valve stem 16. The cam shaft is driven from the engine crankshaft in the conventional manner.

The adjustable tappet 22 (FIGURES 2, 3 and 4) comprises a body 23 formed as a cup-member with a cylindrical recess 24 for the end of the valve stem 16. The base 25 of the cup-member is adapted to be contacted by the cam 21 which thus reciprocates the cup-member and the valve axially against spring pressure in well known manner.

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The cup-member 23 has a bore 26 which is transverse of the valve stem axis, and is slightly inclined thereto. The bore is uniform and is screw-threaded internally.

Inside the threaded bore 26 is a screw-plug 27 threaded to fit therein. It has a tapered flat surface 28 along its length, which, when in position, contacts with and fits flush with the end surface of the valve stem 16 (see FIGURE 3).

The screw-plug 27 can be set in any position within the threaded bore 26; and by means of a screwdriver or key fitting into its slotted or recessed larger end 29 it can be rotated to effect axial movement along the bore 26, and turns to effect clearance adjustment between itself and the valve stem 16 axially along the latter.

Such adjustment is made in steps of one turn of the screw-plug 27 so that its fiat surface 28 is always set in flush contact with the end surface of the valve stem 16. The pitch of the threads and the angular inclination of the axis of the threads are predetermined to effect desired step-wise axial adjustments. Thus various modifications of these relationships are possible.

The base 25 of the cup-member 23 has notches 30 around its rim (FIGURE 4). When the engine is running, the valve is rotated to even out any wear upon its chamfered edge. This rotation is elfected in known manner, as by offsetting the line of contact of the cam 21 upon the tappet 22, or by the twisting of the valve return spring as the valve reciprocates. The valve tappet 22 also rotates. Because of this rotation, the slotted end 29 of the tappet screw-plug 27 may not be accessible through a clear space on the engine cylinder head such that the screw-driver or key can be inserted to effect adjustment of the valve clearance. The notched rim 30 of the cupmember base 25 facilitates convenient finger-tip rotation of the tappet, to bring the screw-plug 27 into position for rotary adjustment.

In a modification (not shown) more than one flat surface is formed on the screw-plug to effect finer adjustments than those effected by one-turn rotations.

I claim:

1. A valve tappet comprising a cup member adapted to fit over the end of a valve stem and having a transverse threaded bore, a threaded plug carried for screw adjusting movement in said bore and having a flat surface along one side adapted to contact the end of the valve stem, said surface lying at an angle with respect to said bore, whereby axial adjustment of said plug in said bore to any of a plurality of positions wherein said flat surface may contact said valve stem, adjusts the effective length of said valve tappet.

2. A valve tappet as defined in claim 1 wherein said threaded plug includes at one end a recess so shaped as to enable rotation of said plug by an externally applied tool.

3. A valve tappet comprising a cup member having a cylindrical recess adapted to fit over and enclose the end of a valve stem, said cup member having a transverse threaded bore intersecting said cylindrical recess and forming an angle with respect to a plane perpendicular to said recess, a threaded plug carried for screw adjustment in said bore and having a flat surface along one side adapted to contact the end of said valve stem, said surface forming an angle with respect to said bore such that upon adjustment of said threaded plug to any of a plurality of positions said surface will lie in a plane perpendicular to said cylindrical recess, such adjustment being effective to determine the effective length of said valve tappet.

4. A valve tappet as defined in claim 3 wherein said threaded plug includes at one end a recess so shaped as to enable rotation of said plug by an externally applied tool.

5. A valve tappet as defined in claim 3 wherein said cup member includes a rim surrounding the end opposite said cylindrical recess and said rim has a plurality of v notches adapted to assist manual rotation of sai cupmemher.

6. A valve tappet as defined in claim 4 wherein said cup member includes a rim surrounding the end opposite said cylindrical recess and said rim has a plurality of notches adapted to assist manual rotation of said cup member.

4 References Cited by the Examiner UNITED STATES PATENTS 1,210,621 1/1917 Fekete 123-90 2,817,326 12/1957 Taylor 12390 2,966,901 1/1961 Stwiorok 12390 3,002,508 10/1961 Barker et al 12390 3,025,841 3/1962 Beck-am 12390 MARK NEWMAN, Primary Examiner.

A. L. SMITH, Assistant Examiner. 

1. A VALVE TAPPET COMPRISING A CUP MEMBER ADAPTED TO FIT OVER THE END OF A VALVE STEM AND HAVING A TRANSVERSE THREADED BORE, A THREADED PLUG CARRIED FOR SCREW ADJUSTING MOVEMENT IN SAID BORE AND HAVING A FLAT SURFACE ALONG ONE SIDE ADAPTED TO CONTACT THE END OF THE VALVE STEM, SAID SURFACE LYING AT AN ANGLE WITH RESPECT TO SAID BORE, WHEREBY AXIAL ADJUSTMENT OF SAID PLUG IN SAID BORE TO ANY OF A PLURALITY OF POSITIONS WHEREIN SAID FLAT SURFACE MAY CONTACT SAID VAVLE STEM, ADJUSTS THE EFFECTIVE LENGTH OF SAID VALVE TAPPET. 